Ch 10 Intro Metabolism Flashcards
Chemical work
Synthesis of complex bio molecules from simpler ones (anabolism)
Transport work
Take up nutrients, export waste & maintain ion balances
Mechanical work
Cell motility and movement of structures within cell.
Energy
Capacity to do work
ATP
Adenosine 5’-triphosphate a high E molecule used as cells energy currency
Thermodynamics
Study of E changes in a system
1st Law of Thermodynamics
E neither created nor destroyed
2nd Law of Thermodynamics
Chemical and physical processes proceed such that Entropy increases
Entropy
Measure of randomness and/or disorder
Exothermic reactions
Give off heat.
Endothermic reactions
Absorb heat
Calorie
Amt of heat E need to raise 1g water 1 degree C
Joules
Units of work capable of being done
Enthalpy
Heat content in a system
Free E change
Amount of E in a system available to do useful work at constant temp and pressure
Reactions occur spontaneously when
The free E of the system decreases
Equilibrium
State where no net change is occurring & free E is at a minimum (forward rxn = reverse rxn)
Equilibrium constant ( Keq)
[C][D] / [A][B]
( >1 then more products than reactants at equilibrium and will proceed as written
Standard free E change (delta G degree)
Free E change for a process at defined conditions of [], pressure, pH, and temp
Delta G degree apostrophe
Standard free E change when pH is 7 ( ie most cells)
= -2.303 RT x log Keq
(R=gas constant T=absolute temp)
Gas Constant (R)
1.9872 cal/ mol-degree
8.3145 J/mol-degree
Exergonic reaction
A rxn than spontaneously goes to completion. Standard free E change is NEGATIVE, Keq > 1
Energy earned
Exergonic reactions ( Neg delta G)
Energy spent
Endergonic reactions ( used by cells to make ATP to “store” E)
ADP
Adenosine diphosphate
Orthophosphate
Pi
High phosphate transfer potential
Phosphorylated compound will readily transfer a phosphoryl grp to another molecule (large release of energy occurs)
Substrate level phosphorylation
Making ATP using phoshoenolpyruvate (PEP) as source for phosphoryl group
Redox reactions
Reactions involving the transfer of electrons from a electron donor to an electron acceptor
e- donor
Also called reducing agent or reductant. Donates the e- to the acceptor in a redox rxn
e- acceptor
Also called oxidizing agent or oxidant. Accepts e- from the donor in a redox rxn.
More e- on a molecule means
More E for that molecule to donate
Conjugate redox pair
e- acceptor and e- donor of redox half reaction
Equilibrium constant for redox half rxn
Standard reduction potential (E0) ( measure of the tendency of the donor half to lose e-, measured in volts)
Redox rxn tower trend
Half Rxn w/ more - E0 pair with half rxn with more + E0 (rxns further apart tend to pair well)
NAD+
Nicotinamide adenine dinucleotide
Electron transport chain (ETC)
Series of e- carriers that work together to transfer e- from donors to acceptors (like O2) AKA electron transport system. Embedded in a membrane.
Molecules involved in ETC
NAD+, NADP+, cytochromes, heme proteins, nonheme proteins, coenzyme Q, flavin adenine dinucleotide (FAD) flavin mononucleotide (FVN)
E0 trend in ETC
1st ETC most negative E0, ea slightly less so spontaneous transfer occurs
Metabolites
Products of the many reactions carried out by the cell
Biochemical pathways
Sets of chemical rxns preformed by organisms that convert starting substrate to one or more products
Metabolite flux
Turnover rate of metabolite ( rate it is produced and then used up)
Enzymes
Protein catalyst
Catalyst
Substance that increases the rate of chemical rxn without being changed permanently
How many general classes of enzymes?
6: Oxidireductase, Transferase, Hydrolase, Lyase, Isomerase, Ligase
Oxidoreductase
Redox reactions
Transferase
Rxns involving transfer of chemical groups between molecules
Hydrolase
Hydrolysis
Lyase
Breaking of bonds by means other than hydrolysis
Isomerase
Rearrange molecules to isomer form
Ligase
Joining two molecules using ATP or other nucleoside triphosphate
Apoenzyme
Enzyme that requires a cofactor
Cofactor
Non protein component required for catalytic activity
Holoenzyme
Complete apoenzyme and cofactor complex
Cofactor tightly (covalently) linked to apoenzyme
Prosthetic group
Loosely attached, able to dissociate cofactor
Coenzyme
Activation energy
Energy required to bring substrate molecules together in correct way for reaction to occur. (reach the transition state complex)
Active site
Aka catalytic site. Location on enzyme where substrate enzyme complex is formed to catalyze the rxn
How do enzymes lower activation energy?
Bind substrates at the active site in the correct orientation for rxn to occur
Michaelis constant (Km)
Substrate concentration required for enzyme to reach half maximal velocity (used to quantify the affinity of enzyme for substrate)
What does lower Km mean?
Lower substrate concentration at which enzyme catalyzes the rxn (low Km=high affinity for substrate
Competitive inhibitor
Molecule that inhibits enzyme function by directly competing with substrate by binding to the active site.
Non competitive inhibitors
Inhibit enzyme function by binding to another site on enzyme that alters the shape of the enzyme, rendering it non functional.
Ribozyme
Catalytic ribosomes
How many ways are metabolic pathways regulated?
3 major ways; metabolic channeling, regulation of gene expression, posttranslational regultation
Metabolic channeling
Localizing metabolites and enzymes in different parts of cells
Compartmentation
Distribution of enzymes an metabolites among separate cell structures or organelles
Regulation of gene expression
Regulates the synthesis of particular enzyme by changing rates of transcription and/or translation to control the amount of enzyme in cell (slow response)
Posttranslational regulation
Direct stimulation or inhibition of enzyme activity, two main types: allosteric reg and covalent mod
Allosteric Regulation
Allosteric enzymes are altered by non covalent binding of molecule (allosteric effector) at regulatory site separate from active site. Causes a change in enzyme conformation at active site that activates or inhibits enzyme
Allosteric effector
Molecule that binds to allosteric enzymes regulatory site to activate or inhibit enzyme function
Regulatory site
Site on allosteric enzyme separate from active site that binds a allosteric effector
Covalent modification
Activation or inhibition of enzyme via covalent addition or removal of particular functional group (phosphoryl, methyl, or adenylyl)
Covalent mod of E.coli glutamine synthetase
Each of 12 subunits can bind adenylic acid———> when all 12 have AMP not active. Removal of AMP allows glutamine formation———> the more removed the more active
Allows for more sophisticated and varied stimuli response
Covalent modification systems
Pacemaker enzyme
An enzyme that catalyzes the slowest (or rate determining) Rxn in a metabolic pathway
Feedback inhibition
Neg feedback mech where end product inhibits the activity of an enzyme in the pathway leading to its formation. Aka end product inhibition
Isoenzymes
Different forms of an enzyme that catalyze the same Rxn. Aka isozymes.